1. Field of the Invention
The present invention relates to a tire vulcanization mold. More particularly, the present invention relates to a tire vulcanization mold that can simplify a machining process associated with forming a venting mechanism and ensure stable ventilation.
2. Background Information
When a tire is vulcanized, unnecessary air can become trapped inside a tire vulcanization mold and gas can be generated by the vulcanization. This air and gas can cause vulcanization failures such as insufficient rubber filling with respect to the tire being vulcanized. Therefore, a venting mechanism is provided in the tire vulcanization mold to vent air and gas generated during vulcanization to an exterior.
An exhaust mechanism is described in Laid-open Japanese Patent Publication No. 2007-38426 (JP2007-38426A) in which a mold is cast by pouring molten metal into a die into which a blade has been inserted such that a small gap is formed between the blade and the mold main body. The small gap forms a portion of a ventilation passage. However, since the small gap is formed by utilizing a difference between the thermal expansion coefficients (thermal contraction) of the blade and the mold main body, the size of the gap tends to vary and presents a disadvantage with respect to obtaining a stable ventilation efficiency.
Another structure for an exhaust mechanism is described in Laid-open Japanese Patent Publication No. 2009-269363 (JP2007-269363A) in which a narrow hole is provided in a tire molding surface and a blade is embedded in the narrow hole so as form a small gap between the blade and a long side of the narrow hole. Air and gas are vented to an exterior of the mold through this small gap. However, both lengthwise end portions of the narrow hole are made to be narrower in width than a middle portion in order to hold both end portions of the blade. More specifically, since the shape of the narrow hole provided in the tire molding surface is irregular and not simple in a plan view, the number of machining steps increases and the machining becomes complex. Also, if the irregularly shaped narrow hole is not machined precisely, then stable ventilation cannot be ensured.